Screwdriver for operating self-tightening screw

ABSTRACT

Screwdriver for operating self-tightening screw, including a grip; a striking mechanism disposed in the grip for providing a striking force; and a stem body slidably disposed in the grip. The top end of the stem body is drivingly engaged with the striking mechanism. The bottom end of the stem body serves to drive the self-tightening screw. In use, the screwdriver is pressed downward against the self-tightening screw. At this time, the stem body is slided into the grip to drivingly move the striking mechanism. The striking mechanism produces a striking force acting on the self-tightening screw so as to nail the self-tightening screw into a screwing position of a work piece. Then the screwdriver is used to screw the self-tightening screw into the work piece.

BACKGROUND OF THE INVENTION

The present invention relates to a screwdriver, and more particularly toa screwdriver for operating self-tightening screw. The screwdriver isable to first nail the self-tightening screw into a screwing position ofa work piece and then further screw the self-tightening screw into thework piece.

In a DIY product, self-tightening screws are often used to connect workpieces with each other, such as wooden slats.

The self-tightening screw is driven by a screwdriver to screw into awork piece. Prior to screwing the self-tightening screw, the tip of theself-tightening screw must be first nailed into the work piece. Thereare generally two measures for nailing the tip of the self-tighteningscrew into the work piece. One is to use a hammering tool to strike andnail the self-tightening screw in to the work piece. The other is todirectly use the screwdriver to exert an axial force onto theself-tightening screw and simultaneously drive the self-tightening screwinto the work piece. With respect to the first measure, an operator mustpinch the self-tightening screw with one hand and at the same timeoperate the hammering tool to strike the self-tightening screw with theother hand so as to nail the self-tightening screw into the work piece.During the striking operation, it often takes place that the hammeringtool incautiously hits and injures the hand pinching the self-tighteningscrew. With respect to the second measure, the pressure exerted by theoperator onto the self-tightening screw is not so direct and effectiveas the pressure produced by the hammering tool so that it is laboriousfor the operator to effectively press the self-tightening screw againstthe work piece. Moreover, the tip of the self-tightening screw contactswith the work piece at a point with small area so that theself-tightening screw contacts with the work piece in an unstable stateand tends to deflect and can be hardly located on the work piece.Therefore, during operation, it often takes place that the screwdriverslips away from the self-tightening screw and the self-tightening screwbounds away to other place. Therefore, it is necessary to repeat theoperation many times for nailing the self-tightening screw into the workpiece.

SUMMARY OF THE INVENTION

It is therefore a primary object of the present invention to provide ascrewdriver for operating self-tightening screw. The screwdriver is ableto first nail the self-tightening screw into a work piece to facilitatethe screwing of the self-tightening screw.

It is a further object of the present invention to provide a screwdriverfor operating self-tightening screw, which is able to first nail theself-tightening screw into work piece without using any other tool andpinching the screw with a hand so that the user's hand is protected frombeing hit and injured.

It is still a further object of the present invention to provide ascrewdriver for operating self-tightening screw, by which during thenailing of the self-tightening screw, the screw will not deflect orrandomly bound away.

It is still a further object of the present invention to provide ascrewdriver for operating self-tightening screw, which enables a user toquickly and conveniently nail a self-tightening screw.

The present invention can be best understood through the followingdescription and accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective exploded view of a first embodiment of thepresent invention;

FIG. 2 is a sectional assembled view of the first embodiment of FIG. 1;

FIG. 3 is a sectional view taken along line 3—3 of FIG. 2, showing arelationship between the stop member and the stem body;

FIG. 4 is a sectional view according to FIG. 3, showing anotherrelationship between the stop member and the stem body;

FIG. 5 shows that a self-tightening screw is to be nailed into a workpiece by the screwdriver of the present invention;

FIG. 6 is a view according to FIG. 5, showing a state in the instantprior to striking the screw;

FIG. 7 is a view according to FIG. 6, showing that the screw is struck;

FIG. 8 is a front partially sectional view of a second embodiment of thepresent invention;

FIG. 9 is a view according to FIG. 8, showing the striking state of thesecond embodiment;

FIG. 10 is a partially sectional view of a third embodiment of thepresent invention;

FIG. 11 is a partially sectional view of a fourth embodiment of thepresent invention;

FIG. 12 is a partially sectional view of,a fifth embodiment of thepresent invention;

FIG. 13 is a partially sectional view of a sixth embodiment of thepresent invention;

FIG. 14 is a view according to FIG. 13, showing the striking state ofthe sixth embodiment of the present invention;

FIG. 15 is a partially sectional view of a seventh embodiment of thepresent invention;

FIG. 16 is a view according to FIG. 15, showing the striking state ofthe seventh embodiment of the present invention;

FIG. 17 is a sectional assembled view of an eighth embodiment of thepresent-invention;

FIG. 18 is a perspective view of a ninth embodiment of the presentinvention;

FIG. 19 is a perspective exploded view of the ninth embodiment of FIG.18;

FIG. 20 is a longitudinal sectional view according to FIG. 18;

FIG. 21 is a sectional view taken along line 21—21 of FIG. 20;

FIG. 22 is a sectional view taken along line 22—22 of FIG. 20;

FIG. 23 is a longitudinal sectional view showing that the ratchetmechanism is disposed in the grip;

FIG. 24 is a sectional view taken along line 24—24 of FIG. 20;

FIGS. 25 and 26 are longitudinal sectional view according to FIG. 20,showing the striking state thereof;

FIGS. 27 and 28 are cross-sectional view according to FIG. 21, showingthat the stem body is engaged;

FIGS. 29 and 30 are longitudinal sectional view according to FIG. 23,showing that the ratchet mechanism: provides a ratchet effect;

FIG. 31 is a side view of a part of the embodiment of FIG. 18;

FIG. 32 is a view according to FIG. 31, showing that rotary cap isturned for replacing a screwdriver head;

FIGS. 33 to 36 are cross-sectional views according to FIG. 21, showingthe operation of a part of the tenth embodiment of the presentinvention;

FIG. 37 is a perspective exploded view of an eleventh embodiment of thepresent invention; and

FIG. 38 is a longitudinal sectional assembled view of the eleventhembodiment of FIG. 37.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Please first refer to FIGS. 1 and 2. According to a first embodiment ofthe present invention, the screwdriver 10 includes:

a grip 20 for a user to hold, the grip 20 being formed with an axialpassage 22 passing through a bottom end of the grip; and

a striking mechanism having a resilient energy-reserving member 25 and astriking assembly 30 and disposed in the passage 22 for providing astriking force. The resilient energy-reserving member 25 has arelatively great coefficient of resilience.

The striking assembly 30 includes:

a hammering body 40 which is a column-like metal body, a bottom end ofthe hammering body 40 being formed with an inward extending shaft hole42, the hammering body 40 being slidably received in the passage 22, oneend of the energy-reserving member 25 abutting against the inner wall ofthe passage, while the other end thereof abutting against the hammeringbody for downward pushing the hammering body, when the hammering body 40is not subject to external force, the hammering body 40 being keptlocated at a locating section 23 of the passage 22;

a hammering bar 50, a top end of the hammering bar 50 being a rodsection 52 with smaller diameter, while a bottom end of the hammeringbar 50 being a striking section 54, a body of the hammering bar 50between the rod section 52 and the striking section 54 being formed witha conic guide sect ion 56 having an upward tapered outer diameter, thehammering bar 50 being slidably received in the passage 22 under thehammering body 40, the maximum outer diameter of the body of thehammering bar being smaller than the inner diameter of the passage 22 sothat in a normal state, the hammering bar will naturally tilt and anangle is contained by the axes of the hammering bar 50 and the passage22, in this embodiment, the passage being formed with a rectifyingsection 24 under the locating section 23 corresponding to the guidesection 56 for rectifying the hammering bar;

a resilient member 57 having less coefficient of resilience and fittedaround the hammering bar 50, one end of the resilient member 57 abuttingagainst the inner wall of the passage, while the other end thereofabutting against the hammering bar, whereby when not subject to externalforce, the hammering bar is kept sliding downward and the rod section 52is prevented from extending into the shaft hole 42; and

a stem body 60, in this embodiment, the stem body 60 having a polygonalcross-section, an inner side of the top end of the stem body 60 beingformed with a recessed stop section 62, a bottom end thereof beingformed with a hexagonal socket 64 for fitting with a screwdriver head 65having a driving section 651. Different screwdriver heads can bereplaceably fitted in the socket 64. The top end of the stem body isslidably fitted into the passage 22. The top end of the stem body isformed with a stop: sect ion 66 engaged with an engaging section 201formed on the inner wall of the passage, serving as a lower stop pointof the sliding of the stem body for preventing the stem body fromdropping out. The bottom end of the hammering bar 50 abuts against thestem body to locate the hammering bar 50. The top face of the stem body60 is formed with an eccentric concave 68 or convex, whereby when thearched striking section 54 contacts with the concave 68, the hammeringbar 50 will be surely deflected. However, the concave 68 is omissible.The hammering bar will still naturally tilt without the concave.

The bottom end of the passage 22 is formed with a hole 202 having ashape identical to that of the cross-section of the stem body 60,whereby a torque can be transmitted from the grip 20 to the stem body60.

A stop member 70 which can have various patterns such as a ring bodyfitted on the circumferential face of the grip for a user's hand torotate. Alternatively, the stop member 70 can be an arched plate body asshown in FIG. 1. The pattern of the stop member is not limited to thepattern of this embodiment. The stop member 70 has an engaging section72 and is disposed at a mounting section 26 formed on thecircumferential face of the bottom end of the grip 20 for a user's handto shift between two positions. The engaging section 72 extends from awindow 28 into the passage 22 corresponding the stop section 62 of thestem body 60 for engaging with the stop section 62. When the stop member70 is shifted to one of the two positions, the engaging section 72 isengaged with the stop section 62 to prevent the stem body from slidingtoward the passage.

When shifted to the other position, the engaging section is disengagedfrom the stop section, permitting the stem body to slide iwnard thepassage.

The present invention provides a preceding operation prior to screwingthe self-tightening screw into a screwing position of the work piece.Before the self-tightening screw 75 is screwed, the stop member 70 isfirst shifted to the second position as shown in FIG. 4, making theengaging section 72 disengaged from the stop section 62 of the stem body60. Then the driving section 651 at front end of the stem body is fittedwith the head 76 of the self-tightening screw 75 as shown in FIG. 5 withthe tip of the self-tightening screw pressed against the surface of thework piece.

Thereafter, the operator downward presses the screwdriver. At this time,the self-tightening screw 75 and the stem body 60 will suffer a reactionforce to slide into the passage 22. The hammering bar 50 and thehammering body 40 are driven to slide toward the top end of the passage22 as shown in FIG. 6. At this time, the energy-reserving member 25 iscompressed to reserve a resilient energy. In a normal state, thehammering bar is tilted so that when the hammering bar pushes thehammering body, the top end of the rod section 52 abuts against thebottom face of the hammering body 40 without inserting into the shafthole 42.

When the operator continuously exerts a force, the members 60, 50, 40are further moved inward so that the resilient energy reserved in theenergy-reserving member 25 is gradually increased. When the guidesection 56 of the hammering bar 50 contacts with the rectifying section24, the hammering bar is guided by the rectifying section 24 togradually deflect to an upright position. At this time, the rod section52 is gradually aligned with the shaft hole 42. In the instant ofalignment of the rod section with the shaft hole, the hammering body 40is free from the pushing force of the hammering bar 50 and the hammeringbar is inserted into the hammering body. In this instant, the hammeringbody is temporarily suspended and the resilient energy of theenergy-reserving member 25 is instantaneously released to act on thehammering body. At this time, the hammering body instantaneously strikesthe hammering bar 50 as shown in FIG. 7. The impacting force istransmitted from the hammering bar 50 to the stem body 60, making thetip of the self-tightening screw 75 nail into the screwing position ofthe work piece.

When the screwdriver is released from the pressing force, theenergy-reserving member 25 restores the hammering body 40 to thelocating section 23 and the resilient member 57 downward pushes thehammering bar 50, making the rod section 52 separate from the shaft hole42 into a state as shown in FIG. 5.

The operation of FIGS. 5 to 7 is repeated several times so as to trulyand fixedly nail the tip of the self-tightening screw 75 into the workpiece by a certain depth.

After the self-tightening screw 75 is nailed, the stop member 70 isshifted to the first position as shown in FIG. 3 and the stop section 62of the stem body 60 is engaged with the engaging section 72 of the stopmember 70. At this time, the stem body is located and prevented fromsliding into the passage and restored to a state as shown in FIG. 2.Then, the screwdriver 10 can be used to screw the self-tightening screw75. The torque is transmitted from the grip to the stem body so that theself-tightening screw 75 can be smoothly screwed into the work piece.

It should be noted that in the embodiment of FIG. 2, the transmission oftorque between the grip and the stem body is achieved by the hole 202and the stem body 60 having polygonal cross-section. However, thetransmission of torque can be achieved otherwise. For example, theengaging section 72 can be engaged with the stop section 62 to provide atransmission effect for the torque. Accordingly, the stem body and thehole 202 is no more necessary to suffer any torque.

Furthermore, in the structure of FIG. 2, the stop member 70 serves tolocate the stem body and prevent the stem body from retracting so as todrive the self-tightening screw. However, the energy-reserving member 25has greater resilient energy so that the stem body is uneasy to retractand slide inward. Therefore, even if the stop member is omitted, thescrewdriver 10 can still drive the self-tightening screw with the stembody.

FIG. 8 shows another embodiment of the present invention, in which thestop member 82 is a rod member formed with a through hole as an engagingsection 83. One end of the stop member 82 extends from the window 81into the grip 80, while the other end thereof protrudes outside the gripand is radially slidable. The stem body 85 is passed through theengaging section 83. A resilient member 88 is compressed between thegrip and the stop member 82 for resiliently pushing the stop memberoutward in a not forced state. Therefore, the engaging section 83 isengaged with the stop section 86 of the stem body 85.

As shown in FIG. 8, when the stop member 82 is positioned at the firstposition, the stem body is engaged and located for driving theself-tightening screw.

When an operator presses the stop member and makes it move to the secondposition as shown in FIG. 9, the engaging section 83 is aligned with thestem body 85 and the stem body 85 is disengaged. At this time, the stembody can slide toward the passage 89 into a state for striking theself-tightening screw.

FIG. 10 shows still another embodiment of the present invention, inwhich the grip 80 is formed with a radial cut 81. This embodimentfurther includes a pressing lever 87 the body of which is pivotallyconnected to the circumferential face of the grip 80. One end of thepressing lever 87 is connected with the stop member 82 for driving thestop member to slide. This embodiment further includes a resilientmember 88 disposed between the pressing lever 87 and the grip. When notsubject to external force, the resilient member 88 serves to resilientlymake the pressing lever 87 keep the stop member 82 at the first positionfor engaging with and locating the stem body.

When the stop member 82 is positioned at the first position, theengaging section 83 is not aligned with the stem body 85 and the passage89 so that the stem body is engaged and located for driving theself-tightening screw.

When the operator presses the pressing lever 87 and drives the stopmember 82 to slide to the second position, the engaging section 83 isaligned with the stem body and disengaged from the stem body. At thistime, the stem body can slide toward the passage 89 for striking theself-tightening screw.

FIGS. 11 and 12 shows two other embodiments of the present invention, inwhich a tilting member 92 is disposed in the grip 90. In FIG. 11, thetilting member is a resilient member extending into the passage 94 forpushing the hammering bar 95, whereby the hammering bar 95 is kepttilted before rectified. The tilting member 92 of the FIG. 11 can be aspring disposed in the grip. In FIG. 12, the tilting member 92 is aresilient rib integrally formed with the grip 90 for pushing thehammering bar.

FIG. 13 shows still another embodiment of the present invention, inwhich the passage 90 is free from the locating section as the firstembodiment. The rectifying section 91 is positioned at a height of thehammering body 92. The inner side of the bottom end of the hammeringbody 92 is formed with a radial tunnel 93 communicating with the shafthole 94. An aligning member 95 is slidably fitted in the tunnel 93. Thebody of the aligning member 95 is formed with a hole 96 corresponding tothe shaft hole 94. The aligning member is positioned under therectifying section 91 by a predetermined distance. A resilient member 97is disposed in the tunnel 93 for pushing the aligning member 95 andmaking one end thereof protrude out of the hammering body in a notforced state. Also, the hole 96 is disaligned from the shaft hole 94.The rod section 99 of the hammering bar 98 extends into the shaft hole94 and abuts against the aligning member 95.

In operation, when the hammering bar 98 and the hammering body 92 sufferexternal force and move inward, the protruding end of the aligningmember 95 contacts with the rectifying section 91 and is guided therebyto move inward along the tunnel 93. In the instant of aligning of thehole 96 with the shaft hole 94, the rod section 99 of the hammering bar98 is totally aligned with the hole 96 without abutting against thealigning member. In this instant, the hammering body 92 is disengagedfrom the hammering bar and the hammering body 92 is driven by theresilient energy of the energy-reserving member to strike the hammeringbar as shown in FIG. 14. At this time, the self-tightening screw suffersa striking force and is nailed into the screwing position.

FIG. 15 shows another embodiment which is different from the embodimentof FIG. 13 in that the passage 91 of the grip 90 is not disposed withthe rectifying section and the circumferential wall of the passage 91 isformed with a slot 93 corresponding to the up and down travel of thealigning member 95. The protruding end of the aligning member 95protrudes from the slot 93 out of the grip for a user's hand to press.In a normal state, the aligning member 95 is pushed by the resilientmember 97 to disalign the hole 96 from the shaft hole 94. The aligningmember 95 is disposed with an engaging section engaged with the grip 90.The engaging section can be a stepped engaging section 901 forpreventing the aligning member 95 from dropping out of the grip.

In operation, when the hammering bar 98 and the hammering body 92 sufferexternal force and upward slide in a direction as shown in the drawings,the energy-reserving member reserves a resilient energy. Thereafter, theoperator can inward press the aligning member 95 to align the hole 96with the shaft hole 94 so as to provide a striking effect as shown inFIG. 16.

FIG. 17 shows still another embodiment of the present invention, inwhich a ratchet mechanism is disposed on the stem body 92 as shown byphantom line A. Alternatively, a ratchet mechanism is disposed on thegrip 90 corresponding to the stem body as shown by phantom line B. Theratchet mechanisms A, B pertain to prior art and will not be furtherdescribed herein. Accordingly, the screwdrivers of the above embodimentshas a ratchet effect. In the case that the ratchet mechanism is disposedin the grip 90 as the ratchet mechanism B, the torque which the grip andthe stem body suffer is bridged by the ratchet mechanism B and notorque-suffering state exists between the hole 941 of the bottom end ofthe passage 94 and the stem body 92.

FIGS. 18, 19 and 20 show a ninth embodiment of the present invention, inwhich the screwdriver 10 includes:

a grip 20 including an outer grip 21 and an inner grip 25 and a rotarycap 23, the rotary cap 23 being formed with a cavity inward extendingfrom bottom face of the rotary cap 23, multiple receptacles 24 beingformed in the cavity for receiving various kinds of screwdriver heads 26such as flat, cross-shaped, plum blossom-shaped and star-shapedscrewdriver heads, two sides of the rotary cap being formed with throughholes 231 for pivotally connecting the rotary cap with two cylindricalsections 221 of two resilient ribs 22 projecting from the top end of theouter grip 21 side by side, the body of the inner grip 25 being fixedlyinserted in a fitting hole 211 of the outer grip 21 by way of tight fit,a head section 28 of bottom end of the inner grip 25 protruding out ofthe outer grip, the inner grip 25 being formed with an axial passage 30passing through the bottom end of the inner grip, the head section 28being formed with two radial slots, the first slot 31 inward extendingand communicating with the passage 30 as shown in FIG. 21, a ring body33 being received in the passage 30 and located at a shoulder section301, a sleeve body 34 being fitted in the passage 30, the circumferenceof the sleeve body 34 being formed with a cut 341 aligned with the firstslot 31, an end cap 36 being fixed disposed at bottom end of the headsection 28 to locate the ring body 33 and the sleeve body 34 in thepassage 30; and

a striking mechanism 40 disposed in the passage 30 for providing astriking force, the striking mechanism 40 being substantially identicalto the above striking mechanism, including:

a resilient energy-reserving member 41 having a relatively greatcoefficient of resilience;

a hammering body 42, a bottom end of the hammering body being formedwith an inward extending shaft hole 43, the hammering body 42 beingslidably received in the passage and resiliently pushed by theenergy-reserving member 41, whereby the bottom end of the hammering bodyis located at a locating section formed by the ring body 33;

a hammering bar 44, a top end of the hammering bar being a rod section45 with smaller diameter, while a bottom end of the hammering bar 44being a striking section 46, an inclined guide section 47 being disposedbetween the rod section 45 and the striking section 46, the hammeringbar 44 being slidably received in the passage 22 under the hammeringbody 42, a resilient member 48 being fitted on the hammering bar 44 fordownward pushing the hammering bar 44, whereby in a normal state, thehammering bar will naturally tilt and the rod section 45 will contactwith the bottom end of the hammering body 42 without extending into theshaft hole 43 thereof;

a stem body 60 having a polygonal cross-section, the top end of the stembody 60 being formed with a groove-like stop section 62, as shown inFIG. 19, the stop section 62 being formed on a member 61 which isfixedly connected with the top end of the stem body, the top end of thestem body 60 extending through the through hole 361 of the end cap 36into the passage 30 and being telescopically slidable along the passage30, the top end of the stem body 60 con contacting with the bottom endof the hammering bar 44, in a normal state, the engaging section 62being right aligned with the first slot 31 and the cut 341 as shown inFIGS. 20, 21, the body of the stem body being clipped by a C-shapedlatch member 65 for engaging with the end cap 36 to prevent the stembody from dropping out of the inner grip 25;

an engaging member 70 which is a substantially U-shaped plate body, twoengaging sections 72, 74 respectively outward projecting from two sidesof the body of the engaging member 70, the engaging member 70 beingreceived in the first slot 31, the body of the engaging member 70 beingstopped by a post-like stop section 311 disposed in the slot 31 andlocated as shown in FIG. 21, the engaging member being shiftable tochange its position, whereby the engaging sections 72, 74 are positionedin the slot 31 or extend into the passage 30;

a ratchet mechanism 80 including: two tunnels 82 axially formed in thehead section 28 and communicating with the second slot 32 as shown inFIG. 22; two detents 83, 84 each having a ratchet 85 at bottom end, thedetents 83, 84 being slidably received in the two tunnels 82; tworesilient members 86 respectively disposed in the tunnels 82 as shown inFIG. 23 for resiliently pushing the detents, whereby in a not forcedstate, the detents are kept sliding downward, when the detents areresiliently pushed, the wider bodies thereof being stopped in thetunnels without detaching therefrom, the ratchet 85 downward protrudingout of the end cap 36 from the through hole 362 thereof; and an engagingdisc 87 which is formed with a central polygonal engaging hole 88,multiple engaging perforations 89 being formed along the outercircumference of the engaging hole 88 at equal intervals, the engagingdisc 87 being received in a barrel 90 and located right under the headsection 28, the stem body 60 extending through the engaging hole 88 asshown in FIGS. 23, 24 and engaging with the engaging hole 88 as shown inFIG. 24, the ratchets 85 of the detents being engaged in two engagingperforations 89; and

a rotary controlling member which is the above barrel 90, the barrel 90being fitted on the head section 28 for locating the engaging disc 87under the head section and keeping the engaging disc 87 drivinglyconnected with the stem body and the detents, the barrel 90 beingrotatable around the outer circumference of the head section 28, theinner circumferential wall of the barrel being disposed with threelocating sections 91, 92, 93, a locating assembly 29 embedded in thehead section 28 abutting against the locating sections to locate thebarrel, two driving sections 95, 96 which are insertion pins in thisembodiment; being inserted in the circumferential wall of the barrel andprojecting from the inner circumferential face of the barrel, the firstdriving section 95 extending into the first slot 31 as shown in FIG. 21for driving the engaging member 70, the second driving section 96extending into the second slot 32 as shown in FIG. 22 for driving thetwo detents 83, 84.

FIG. 20 shows the use of this embodiment. A suitable screwdriver head 26is installed at the front end of the stem body 60 and aligned with aself-tightening screw 102. A screw-clamping mechanism 100 can beadditionally mounted on the system body as shown by the phantom line forclamping the self-tightening screw, whereby the self-tightening screw isstruck by the screwdriver 10 and nailed into the screwing position. Theclamping mechanism 100 is not the subject of this invention and thuswill not be further described herein.

When it is desired to strike the self-tightening screw, the barrel 90 isfirst turned to a first position as shown in FIG. 21, whereby the firstlocating section 91 is located by the locating assembly 29. At thistime, the engaging member 70 is driven by the first driving section 95to the central position where the two engaging sections 72, 74 will notextend into the passage 30, whereby the stop section 62 of the stem body60 is not engaged with the engaging member 70 and is slidable. Also, asshown in FIGS. 22 and 23, the second driving member 96 is positionedbetween the two detents 83, 84 without driving any of them. At thistime, both the ratchets 85 of the detents are engaged in two engagingperforations 89 of the engaging disc 87 as shown in FIGS. 23, 24 so thatthe engaging member cannot be rotated. Also, the circumference of thestem body 60 is engaged in the engaging hole 88 of the engaging disc 87without rotating. Therefore, at this time, the ratchet mechanism 80 isunable to provide a ratchet effect.

Then, as shown in FIG. 25, the tip of the self-tightening screw 102 ispressed against the surface of the work piece and the operator furtherdownward presses the screwdriver. At this time, the stem body 60 slidesinto the passage 30 and the hammering bar 44 and the hammering body 42are driven to move into the passage 30 to compress the energy-reservingmember 41 for reserving a resilient energy.

When the operator further exerts a force onto the screwdriver, themembers 60, 44, 42 are further moved inward to increase the resilientenergy reserved in the energy-reserving member 41. When the guidesection 47 of the hammering bar 44 contacts with the rectifying section331 formed by the bottom edge of the inner hole of the ring body 33, thehammering bar is guided to gradually deflect to an upright position. Inthe instant of alignment of the rod section 45 with the shaft hole 43 ofthe hammering body 42, the hammering body is free from the pushing forceof the hammering bar 44 and the hammering bar is inserted into thehammering body. In this instant, the resilient energy of theenergy-reserving member 41 is instantaneously released to act on thehammering body. At this time, the hammering body instantaneously strikesthe hammering bar 44 as shown in FIG. 26. The impacting force acts onthe stem body 60, making the tip of the self-tightening screw 102 nailedinto the work piece.

When the screwdriver is released from the pressing force, the grip 20 isslightly moved upward and the resilient member 48 downward pushes thehammering bar 44 and the stem body 60, whereby the striking mechanism 40is restored to a state as shown in FIG. 20.

The operation of FIGS. 20, 25 and 26 is repeated several times so as totruly and fixedly nail the tip of the self-tightening screw into thework piece by a certain depth.

After the self-tightening screw is nailed, the barrel 90 is turned tothe second position as shown in FIG. 27 where the second locatingsection 92 is located by the locating assembly 29. At this time, theengaging member 70 is driven by the first driving section 95 anddeflected, making the first engaging section 72 extend into the passage30 to engage with the stop section 62 of the stem body 60. At this time,the stem body is engaged and fixed without sliding and the stem body canexert an axial force onto the self-tightening screw. Also, when thebarrel is located at the second position, as shown in FIG. 29, thesecond driving section 96 pushes an inclined push section 831 disposedon the body of the first detent 83, making the detent 83 slide into thetunnel 82. At this time, the ratchet 85 is moved out of the engagingperforation 89 of the engaging disc 87 and only the ratchet 85 of thesecond detent 84 remains engaged in the engaging perforation of theengaging disc. Therefore, the first detent 83 is unable to act on theengaging disc 87.

The state of FIG. 29 provides a one-way ratchet effect. According to thedirection of the drawing, when the engaging disc 87 is moved left, theratchet 85 (vertical face thereof) of the second detent 84 will beengaged in the engaging perforation 89, we preventing the engaging discfrom moving toward left corner. Accordingly, under such circumstance,when the grip is turned, the engaging disc 87 will drive the stem body60 to rotate for screwing the screw. Reversely, when the engaging discis moved right, the engaging perforation 89 thereof will push theinclined face 851 of the ratchet 85 of the detent 84, making the detent84 slide into the tunnel 82 as shown by the phantom line. At this time,the ratchet of the detent is disengaged from the engaging perforation89, permitting the engaging disc to move toward the right corner. Undersuch circumstance, when turning the grip, the engaging disc 87 will idleand the stem body cannot drive the screw.

When the barrel 90 is rotated to the third position, as shown in FIG.28, the third locating section 93 is located by the locating assembly29. At this time, the engaging member 70 is driven and deflected by thefirst driving section 95 and the second engaging section 74 is engagedwith the stop section 62 of the stem body 60 for fixing the stem body.Also, the second driving section 96 as shown in FIG. 30 pushes theinclined push section 841 of the second detent 84, making the detent 84slide into the tunnel 82. At this time, the ratchet 85 of the detent isdisengaged from the engaging perforation 89 of the engaging disc andonly the ratchet 85 of the first detent 83 remains engaged in theengaging disc.

The state of FIG. 30 provides a one-way ratchet effect in anotherdirection. When the engaging disc 87 is moved right, the ratchet 85 ofthe first detent 83 will be engaged in the engaging perforation 89,preventing the engaging disc from moving toward right corner.Accordingly, under such circumstance; when the grip is turned, the stembody 60 can screw the screw. Reversely, when the engaging disc is movedleft, the engaging perforation 89 thereof will push the inclined face851 of the ratchet 85 of the detent 83, making the detent 83 slide intothe tunnel 82 as shown by the phantom line. At this time, the engagingdisc can move toward the left corner. Under such circumstance, whenturning the grip, the engaging disc 87 will idle and the stem bodycannot drive the screw.

By means of the above one-way ratchet effect, the screwdriver cantighten or untighten the screw.

Multiple shapes and sizes of screwdriver heads 26 are loaded in therotary cap 23 disposed on the grip 20 as shown in FIG. 31 for a user tochoose. When replacing the screwdriver head, the rotary cap 23 is turnedleft or right and opened as shown in FIG. 32 to expose the bottomopening of the rotary cap. Then, a necessary screwdriver head 26 istaken out from the receptacle 24 to fit with the bottom end of the stembody for use. Thereafter, the rotary cap is turned back to the closeposition as shown in, FIG. 31 and located. There can be two types offixing structures for the rotary cap. One includes a projecting section232 formed on the bottom edge of the rotary cap and a recessed section201 formed on the top edge of the grip 20. The projecting section 232 islatched in the recessed section 201 to locate the rotary cap. The otheris such that, as shown in FIG. 31, the edge of the end of eachcylindrical section 221 is disposed with several projections 222, whilethe circumference of the through hole 231 of the rotary cap is disposedwith several recesses 233. Two press buttons 105 are inserted with thecylindrical sections 221 from outer sides of the through hole. When therotary cap 23 is positioned in a close position, the projections 222 areengaged in the recesses 233. When it is desired to turn open the rotarycap, the two press buttons 105 are pressed inward to inward deflect thetwo resilient ribs 22. At this time, the projections 222 are disengagedfrom the recesses 233 of the rotary cap, permitting the rotary cap to beturned open. When the rotary cap is turned back, the ribs 22 areresiliently restored to again fix the rotary cap.

FIGS. 33 to 36 show a tenth embodiment which is substantially identicalto that of FIG. 21. Only the barrel, engaging member and stem body ofthis embodiment are shown. The other components of this embodiment areidentical to those of the ninth embodiment.

In this embodiment, the barrel 120 has four stages of locatingpositions. When the first locating section 121 of the barrel is locatedby the locating assembly 115 in the grip 110 as shown in FIG. 33, theengaging member 130 is located by the first driving section 126 at thecenter. At this time, the two engaging sections 132, 134 of the engagingmember are disengaged from the stop section 136 of the stem body 135 sothat the stem body 135 can slide into the grip for providing a strikingeffect. The second driving section of the barrel will not drive the twodetents so that no ratchet effect is provided.

When the second locating section 122 of the barrel 120 is located by thelocating assembly 115 as shown in FIG. 34, the engaging member 130 isdriven and deflected by the first driving section 126, whereby the firstengaging section 132 is engaged with the stop section 136 of the stembody 135. At this time, the stem body cannot move inward and is unableto provide a striking effect. Also, the second driving section of thebarrel will not drive the two detents so that no ratchet effect isprovided. At this time, the stem body can exert an axial force onto thescrew and when the grip 110 is turned in any direction, the stem body issynchronously rotated to tighten or untighten the screw.

When the third locating section 123 of the barrel 120 is located by thelocating assembly 115 as shown in FIG. 35, the first engaging section132 of the engaging member 130 is still engaged with the stop section136 of the stem body 135 so that the stem body cannot provide a strikingeffect. Also, the second driving section of the barrel will drive one ofthe detents to provide a one-way ratchet effect.

When the fourth locating section 124 of the barrel 120 is located by thelocating assembly 115 as shown in FIG. 36, the second engaging section134 of the engaging member 130 is engaged with the stem body 135 so thatthe stem body cannot provide a striking effect. Also, the second drivingsection of the barrel will drive the other of the detents to provide aone-way ratchet effect in another direction.

FIGS. 37 and 38 show an eleventh embodiment of the present invention,which is almost entirely identical to the ninth embodiment and onlylittle difference exists therebetween.

In this embodiment, the grip 20 is free from the first slot 31 and thestop section 311, the sleeve body 34 is free from the cut, 341, the stembody 60 is free from the stop section 62 and the barrel 90 is free fromthe driving section 95 and the engaging member 70.

In use, as shown in FIG. 38, in a not striking state, the screwdriver 10can still drive the self-tightening screw 102. Even if the screwdriverof this embodiment is in the striking state as shown in FIG. 26, it canbe still used to screw the self-tightening screw.

The present invention has the following functions:

1. The primary function of the, screwdriver of the present invention isto nail the self-tightening screw at a screwing position. Therefore, thescrewdriver of the present invention has double effects of nailing thescrew and screwing the screw. After the self-tightening screw is nailed,the self-tightening screw can be screwed. This is convenient to a user.

2. The nailing of the self-tightening screw is directly achieved by thescrewdriver without using any other hammering tool and without pinchingthe self-tightening screw with a hand. Therefore, the hand is protectedfrom being hit and injured by the hammering tool and the safety inoperation can be ensured. Moreover, the present invention enables a userto screw the self-tightening screw with one single hand so that theoperation is facilitated.

In addition, the screwdriver of the present invention is able to providea striking effect so that a suitable tool can be installed at the frontend of the stem body to provide a punching effect.

The above embodiments are only used to illustrate the present invention,not intended to limit the scope thereof. Many modifications of the aboveembodiments can be made without departing from the spirit of the presentinvention.

What is claimed is:
 1. Screwdriver for operating a self-tighteningscrew, comprising: a grip for a user to hold, the grip being formed withan axial passage passing through a bottom end of the grip; a strikingmechanism disposed in the passage for providing a striking force actingonto the bottom end of the grip; and a step body, a top end of the stembody being slidably disposed in the passage without dropping out, abottom end of the stem body protruding out of the grip for engaging witha self-tightening screw, a torque being transmitted between the stembody and the grip, the top end of the stem body being drivinglyconnected with the striking mechanism, a striking force provided by thestriking mechanism acting on the stem body, wherein an inner side of thetop end of the stem body has a stop section, the screwdriver furthercomprising a stop member having an engaging section, the stop memberbeing disposed on a circumferential face of the grip and movable betweentwo positions, whereby when the stop member is positioned at a firstposition, the engaging section is engaged with the stop section tolocate the stem body, while when the stop member is positioned at asecond position, the stop section is disengaged from the engagingsection, permitting the stem body to slide, whereby, when theself-tightening screw is engaged with the stem body and the screwdriveris pressed downward against the self-tightening screw, making theself-tightening screw and the stem body move toward the passage, thestriking mechanism provides the striking force which acts on theself-tightening screw to nail the self-tightening screw into a screwingposition of a work piece and then the screwdriver can be turned to screwthe self-tightening screw into the work piece.
 2. Screwdriver foroperating self-tightening screw as claimed in claim 1, wherein thestriking mechanism includes an energy-reserving member disposed in thepassage and a striking assembly slidably disposed in the passage, whenthe striking assembly suffers an external force to slide inward thepassage, the energy-reserving member reserving a resilient energy whichis transmitted to the striking assembly, after the striking assemblyslides through a predetermined distance, the energy-reserving, memberreleasing the resilient energy to provide a downward striking force, ina not forced state, the striking assembly being positioned at a lowerstop point of the sliding travel thereof.
 3. Screwdriver for operatingself-tightening screw as claimed in claim 1, wherein the circumferentialface of the bottom end of the grip is formed with a window communicatingwith the passage, the engaging section extending from the window intothe passage.
 4. Screwdriver for operating self-tightening screw asclaimed in claim 3, wherein the stop member is an arched plate bodyhaving an engaging section.
 5. Screwdriver for operating self-tighteningscrew as claimed in claim 3, wherein the stop member is a ring body, aninner circumferential wall of the ring body being disposed with anengaging section, the stop member being fitted around the outercircumference of the grip for a user's hand to turn.
 6. Screwdriver foroperating self-tightening screw as claimed in claim 1, wherein thepassage is formed with a hole at the bottom end of the grip, the holehaving a cross-section with a shape corresponding to the shape of thecross-section of the stem body.
 7. Screwdriver for operatingself-tightening screw as claimed in claim 1, further comprising aratchet mechanism disposed on the stem body to provide a ratchet effectfor the screwdriver.
 8. Screwdriver for operating self-tightening screwas claimed in claim 1, further comprising a ratchet mechanism disposedbetween the grip and the stem body to provide a ratchet effect for thescrewdriver and serve as a torque transmitting mechanism between thegrip and the stem body.
 9. Screwdriver for operating self-tighteningscrew as claimed in claim 3, wherein the stop member is a rod member, abody of the stop member being formed with an engaging section, one endof the stop member extending from the window into the grip, while theother end thereof protruding outside the grip and being radiallyslidable, the stem body being passed through the stop member, aresilient member being disposed between the grip and the stop member forresiliently pushing the stop member outward from the grip in a notforced state, whereby the engaging section is engaged with the stopsection of the stem body.
 10. Screwdriver for operating self-tighteningscrew as claimed in claim 3, wherein the grip is formed with a radialcut and the stop member is a rod member passed through the radial cut ofthe grip and radially slidable, the stem body being passed through thestop member, the screwdriver further comprising a pressing lever thebody of which is pivotally connected to the circumferential face of thegrip and movable between two positions, one end of the pressing leverbeing connected with the stop member for driving the stop member toslide, the screwdriver further comprising a resilient member disposedbetween the pressing lever and the grip, when the pressing lever is notsubject to external force, the resilient member serving to resilientlymake the pressing lever keep the stop member at the first position forengaging with and locating the stem body, when the stop member isshifted to the second position, the stop member is disengaged from thestem body.
 11. Screwdriver for operating self-tightening screw asclaimed in claim 1, wherein the bottom end of the stem body is ascrewdriver head.
 12. Screwdriver for operating self-tightening screw asclaimed in claim 1, wherein the bottom end of the stem body is formedwith a socket in which a screwdriver head is fitted.
 13. Screwdriver foroperating self-tightening screw as claimed in claim 2, wherein theenergy-reserving member is disposed at the top end of the passage, thestriking assembly including: a hammering body disposed under theenergy-reserving member and pushed thereby; and a hammering bar disposedunder the hammering body, whereby when the striking assembly slidesinward, the energy-reserving member is compressed and during thesliding, the relationship between the hammering body and the hammeringbar is changed from an engaged state into an insertion state so as torelease the resilient energy reserved in the energy reserving member.14. Screwdriver for operating self-tightening screw as claimed in claim13, wherein a bottom end of the hammering body is formed with an inwardextending shaft hole and a top end of the hammering bar is a rod sectionwith smaller diameter, in a normal state, the rod section being notfitted into the shaft hole, while after the striking assembly slidesinward by a predetermined travel, the rod section being inserted intothe shaft hole for releasing the resilient energy.
 15. Screwdriver foroperating self-tightening screw as claimed in claim 14, wherein theinner wall of the passage is formed with a guide section and the body ofthe hammering bar is formed with a rectifying section under the rodsection on lower side of the guide section, the hammering bar beingtilted in the passage rather than in an upright state, when thehammering bar pushes the hammering body to slide upward, the top end ofthe rod section abutting against the bottom end of the hammering body,when the guide section contacts with the rectifying section, thehammering bar being rectified into an upright state with the rod sectionaligned with the shaft hole for inserting therein to, a resilient memberbeing disposed between the grip and the hammering bar for downwardpushing the hammering bar, whereby when not forced, the hammering bar isrestored to a state in which the hammering bar abuts against thehammering body.
 16. Screwdriver for operating self-tightening screw asclaimed in claim 15, wherein the diameter of the hammering bar issmaller than the inner diameter of the passage for tilting the hammeringbar.
 17. Screwdriver for operating self-tightening screw as claimed inclaim 15, further comprising a tilting member disposed in the grip andresiliently abutting against the hammering bar, whereby prior torectifying, the hammering bar is kept tilted.
 18. Screwdriver foroperating self-tightening screw as claimed in claiming 14, wherein thebottom end of the hammering body is formed with a radial tunnelcommunicating with the shaft hole, the screwdriver further comprising analigning ember slidably fitted in the tunnel, a body of the aligningmember being formed with a hole corresponding to the shaft hole, aresilient member being disposed between the hammering body and thealigning member for resiliently pushing the aligning member to slideoutward from the tunnel and making the hole disaligned from the shafthole, the rod section of the hammering bar abutting against the aligningmember from the bottom end of the shaft hole, whereby after thehammering bar and the hammering body are moved upward by a predetermineddistance, the aligning member is slided into the tunnel to make the holealigned with the shaft hole, permitting the rod section to insert intothe shaft hole.
 19. Screwdriver for operating self-tightening screw asclaimed in claim 18, wherein the wall face of the passage is formed witha rectifying section, one of the aligning member protruding out of thehammering body, whereby when the hammering body is moved upward and thealigning member contacts with the rectifying section, the aligningmember is guided by the rectifying section to slide into the tunnel. 20.Screwdriver for operating self-tightening screw as claimed in claim 18,wherein the circumferential wall of the grip is formed with a slotcorresponding to the up and down travel of the aligning member, one endof the aligning member protruding out of the grip from the slot for auser's hand to press and make the aligning member slide into the tunnel.21. Screwdriver for operating self-tightening screw as claimed in claim15, wherein the circumferential wall of the passage is disposed with alocating section above the guide section, the lower travel of thehammering body being located at the locating section, the resilientmember making the hammering bar located at the lowers top point andmaking the rod section separate from the shaft hole.
 22. Screwdriver foroperating self-tightening screw comprising: a grip formed with an axialpassage passing through a bottom end of the grip; a striking mechanismdisposed in the passage for providing a striking force due to externalforce; a stem body slidably disposed in the passage, a bottom end of thestem body protruding out of the grip, a top end of the stem body beingdrivingly connected with the striking mechanism, whereby when the stembody suffers a force to slide into the passage, the striking forceprovided by the striking mechanism acting on the stem body; a rotarycontrolling member disposed on the grip for a user's hand to shift; anengaging member disposed between the stem body and the rotarycontrolling member; and a ratchet mechanism disposed between the gripand the stem body, whereby when operating the rotary controlling member,the rotary controlling member is drivingly connected with the engagingmember and the ratchet mechanism, the rotary controlling membercooperating with the engaging member to fix the stem body and preventthe stem body from being drivingly connected with the striking mechanismor disengage the stem body and control whether the ratchet mechanismprovides a ratchet effect for the stem body.
 23. Screwdriver foroperating self-tightening screw as claimed in claim 22, wherein therotary controlling member has two driving sections, the first drivingsection corresponding to the engaging member, while the second drivingsection corresponding to the ratchet mechanism, the first drivingsection controlling the shifting of the engaging member, making theengaging member engaged with the stem body or disengaged herefrom, thesecond driving section switching the ratchet mechanism between a ratcheteffect-providing state and a not providing state.
 24. Screwdriver foroperating self-tightening screw as claimed in claim 22, wherein theengaging member is directly connected with the rotary controlling memberand movable along therewith.
 25. Screwdriver for operatingself-tightening screw as claimed in claim 22, wherein the body of thestem body is disposed with a stop section, when the engaging member ismoved to engage with the stop section, the stem body is located. 26.Screwdriver for operating self-tightening screw as claimed in claim 22,wherein the circumferential wall of the grip is formed with a radialfirst slot communicating with the passage, the body of the stem bodybeing disposed with a stop section, in a natural state, when the stembody is not forced, the stop section being aligned with the first slot,the engaging member being movably disposed in the slot, the engagingmember being driven by the rotary controlling member to extend into thepassage and engage with the stop section or driven by the rotarycontrolling member to disengage from the stop section.
 27. Screwdriverfor operating self-tightening screw as claimed in claim 26, wherein therotary controlling member is disposed with a first driving sectionpositioned in the first slot for driving the engaging member to shift.28. Screwdriver for operating self-tightening screw as claimed in claim22, wherein the ratchet mechanism is disposed in the grip, the gripbeing formed with a second slot communicating with the interior of theratchet mechanism, the rotary controlling member being disposed with asecond driving section positioned in the second slot, when operating therotary controlling member, the second driving section switching theratchet mechanism between a ratchet effect-providing state and a notproviding state.
 29. Screwdriver for operating self-tightening screw asclaimed in claim 22, wherein the grip is formed with a first and asecond radial slots, the first slot communicating with the passage, thebody of the stem body being disposed with a stop section correspondingto the first slot, the engaging member being disposed in the first slot,the ratchet mechanism being disposed in the grip, the second slotcommunicating with the ratchet mechanism, the stem body extending intothe ratchet mechanism, whereby the ratchet mechanism provides a ratcheteffect for controlling the operation of the stem body, the rotarycontrolling member having two driving section, the first driving sectionbeing positioned in the first slot for controlling the engaging memberto engage with the stop section, the second driving section beingpositioned in the second slot for switching the ratchet mechanismbetween a ratchet effect-providing state and a not providing state. 30.Screwdriver for operating self-tightening screw as claimed in claim 26,wherein two sides of the body of the engaging member are respectivelydisposed with two engaging sections, when the engaging member is shiftedto one position, the engaging sections being kept in the first slotwithout engaging with the stem body, when the engaging member is shiftedto the other position, one of the engaging sections being engaged withthe stop section of the stem body.
 31. Screwdriver for operatingself-tightening screw as claimed in claim 23, wherein the stem body hasa polygonal cross-section, the ratchet mechanism including: two tunnelsaxially formed in the grip; two detents each having a ratchet at bottomend, the detents being slidably received in the two tunnels; tworesilient members respectively disposed in the tunnels for resilientlypushing the detents, whereby in a not forced state, the detents are keptsliding downward; and an engaging disc which is formed with a centralpolygonal engaging hole, multiple engaging perforations being formedalong the circumference of the engaging hole at equal intervals, theengaging disc being disposed under the detents, the stem body extendingthrough the engaging hole to engage with the stem body, the ratchets ofthe detents being engaged in two engaging perforations of the engagingdisc, the rotary controlling member having at least three shiftingpositions, whereby when the rotary controlling member is shifted to oneof the positions, the second driving section will not drive the twodetents and when the rotary controlling member is shifted to the otherposition, one of the detents is pushed upward and the ratchet thereof isdisengaged from the engaging perforation of the engaging disc. 32.Screwdriver for operating self-tightening screw as claimed in claim 31,wherein the rotary controlling member is a barrel fitted on the grip.33. Screwdriver for operating self-tightening screw as claimed in claim22, wherein-the striking mechanism includes an energy reserving memberdisposed in the passage and a striking assembly slidably disposed in thepassage, when the striking assembly is driven by the stem body to slideinwards the passage, the energy-reserving member reserving a resilientenergy, after the striking assembly slides through a predetermineddistance, the energy-reserving member releasing the resilient energy toprovide a downward striking force which is transmitted from thestriking-assembly to the stem body, in a not forced state, the strikingassembly being positioned at a lower stop point of the sliding travelthereof.
 34. Screwdriver for operating self-tightening screw as claimedin claim 33, wherein the striking assembly including: a hammering bodydisposed under the energy-reserving member and pushed thereby; and ahammering bar disposed under the hammering body to abut against thehammering body, whereby when the striking assembly slides inward, theenergy-reserving member is compressed and during the sliding, thehammering body and the hammering bar is released from the engaged stateso as to release the resilient energy.
 35. Screwdriver for operatingself-tightening: screw as claimed in claim 34, wherein a bottom end ofthe hammering body is formed with an inward extending shaft hole and atop end of the hammering bar is a rod section with smaller diameter, ina normal state, the rod section being not fitted into the shaft hole,while after the striking assembly slides inward by a predeterminedtravel, the rod section being inserted into the shaft hole for releasingthe resilient energy.
 36. Screwdriver for operating self-tighteningscrew as claimed in claim 35, wherein the inner wall of the passage isformed with a guide section and the body of the hammering bar is formedwith a rectifying section under the rod section on lower side of theguide section, when the hammering bar pushes the hammering body to slideupward, the top end of the rod section abutting against the bottom endof the hammering body, when the guide section contacts with therectifying section, the hammering bar being rectified into an uprightstate with the rod section aligned with the shaft hole for insertingtherein to, a resilient member being disposed between the grip and thehammering bar for downward pushing the hammering bar, whereby when notforced, the hammering bar is restored to a state in which the hammeringbar abuts against the hammering body.
 37. Screwdriver for operatingself-tightening screw as claimed in claim 31, wherein the grip includesan outer grip formed with a fitting hole and an inner grip having a headsection at bottom end, the inner grip being fixedly disposed in thefitting hole, the head section being exposed outside the bottomend ofthe outer grip, the passage being formed in the inner grip, the ratchetmechanism and the rotary controlling member being disposed at the headsection.
 38. Screwdriver for operating self-tightening screw as claimedin claim 22, wherein at least two rib sections project from the top endof the grip, the screwdriver further comprising a rotary cap, the rotarycap being formed with a cavity inward extending from bottom face of therotary cap, multiple receptacles being formed in the cavity forreceiving various kinds of screwdriver heads, the rotary cap beingpivotally connected with the rib sections.
 39. Screwdriver for operatingself-tightening screw comprising: a grip formed with an axial passagepassing through a bottom end of the grip; a striking mechanism disposedin the passage for providing a striking force acting onto the bottom endof the grip due to external force; a stem body slidably disposed in thepassage, a bottom end of the stem body protruding out of the grip, a topend of the stem body being drivingly connected with the strikingmechanism, whereby when the stem body suffers an external force to slideinto the passage, the striking mechanism providing the striking forceacting on the stem body; a rotary controlling member disposed on thegrip for a user's hand to shift; and a ratchet mechanism disposedbetween the grip and the stem body; whereby when operating the rotarycontrolling member, the rotary controlling member is drivingly connectedwith the ratchet mechanism to control whether the ratchet mechanismprovides a ratchet effect for the stem body.
 40. Screwdriver foroperating self-tightening screw as claimed in claim 39, wherein therotary controlling member has a driving section, the driving sectioncorresponding to the ratchet mechanism, the-driving section beingdrivingly connected with the ratchet mechanism to control the ratcheteffect of the ratchet mechanism.
 41. Screwdriver for operatingself-tightening screw as claimed in claim 39, wherein the ratchetmechanism is disposed in the grip, the grip being formed with a slotcommunicating with the interior of the ratchet mechanism, the rotarycontrolling member being disposed with a driving section positioned inthe slot, when operating the rotary controlling member, the drivingsection switching the ratchet mechanism between a ratcheteffect-providing state and a not providing state.
 42. Screwdriver foroperating self-tightening screw as claimed in claim 39, wherein theratchet mechanism is disposed in the grip, the stem body extending intothe ratchet mechanism, whereby the ratchet mechanism provides a ratcheteffect for controlling the operation of the stem body, the grip beingformed with a radial slot communicating with the ratchet mechanism, therotary controlling member having a driving section positioned in theslot for switching the ratchet mechanism between a ratcheteffect-providing state and a not providing state.
 43. Screwdriver foroperating self-tightening screw as claimed in claim 40, wherein the stembody has a polygonal cross-section, the ratchet mechanism including: twotunnels axially formed in the grip; two detents each having a ratchet atbottom end, the detents being slidably received in the two tunnels; tworesilient members respectively disposed in the tunnels for resilientlypushing the detents, whereby in a not forced state, the detents are keptsliding downward; and an engaging disc which is formed with a centralpolygonal engaging hole, multiple engaging perforations being formedalong the circumference of the engaging hole at equal intervals, theengaging disc being disposed under the detents, the stem body extendingthrough the engaging hole to engage with the stem body, the ratchets ofthe detents being engaged in two engaging perforations of the engagingdisc, the rotary controlling member having at least three shiftingpositions, whereby when the rotary controlling member is shifted to oneof the positions, the second driving section will not drive the twodetents and the two detents are kept engaged with the engaging disc andwhen the rotary controlling member is shifted to the other position, oneof the detents is pushed upward and the ratchet thereof is disengagedfrom the engaging perforation of the engaging disc.
 44. Screwdriver foroperating self-tightening screw as claimed in claim 39, wherein therotary controlling member is a barrel fitted on the grip. 45.Screwdriver for operating self-tightening screw as claimed in claim 39,wherein the striking mechanism includes an energy-reserving memberdisposed in the passage and a striking assembly slidably disposed in thepassage, when the striking assembly is driven by the stem body to slideinward the passage, the energy-reserving member reserving a resilientenergy, after the striking assembly slides through a predetermineddistance, the energy-reserving member releasing the resilient energy toprovide a downward striking force which is transmitted from the strikingassembly to the stem body, in a not forced state, the striking assemblybeing positioned at a lower stop point of the sliding travel thereof.46. Screwdriver for operating self-tightening screw as claimed in claim45, wherein the striking assembly including: a hammering body disposedunder the energy-reserving member and pushed thereby; and a hammeringbar disposed under the hammering body to abut against the hammeringbody, whereby when the striking assembly slides inward, theenergy-reserving member is compressed and during the sliding, thehammering body and the hammering bar is released from the engaged stateso as to release the resilient energy.
 47. Screwdriver for operatingself-tightening screw as claimed in claim 46, wherein a bottom end ofthe hammering body is formed with an inward extending shaft hole and atop end of the hammering bar is a rod section with smaller diameter, ina normal state, the rod section abutting against the bottom end of thehammering body and being not fitted into the shaft hole, while after thestriking assembly slides inward by a predetermined travel, the rodsection being inserted into the shaft hole for releasing the resilientenergy.
 48. Screwdriver for operating self-tightening screw as claimedin claim 47, wherein the inner wall of the passage is formed with aguide section and the body of the hammering bar is formed with arectifying section under the rod section on lower side of the guidesection, when the hammering bar pushes the hammering body to slideupward, the top end of the rod section abutting against the bottom endof the hammering body, when the guide section contacts with therectifying section, the hammering bar being rectified into an uprightstate with the rod section aligned with the shaft hole for insertingtherein to, a resilient member being disposed between the grip and thehammering bar for downward pushing the hammering bar, whereby when notforced, the hammering bar is restored to a state in which the hammeringbar abuts against the hammering body.
 49. Screwdriver for operatingself-tightening screw as claimed in claim 39, wherein the grip includesan outer grip formed with a fitting hole and an inner grip fixedlydisposed in the fitting hole, the passage being formed in the innergrip.
 50. Screwdriver for operating self-tightening screw as claimed inclaim 43, wherein the grip includes an outer grip formed with a fittinghole and an inner grip having a head section at bottom end, the innergrip being fixedly disposed in the fitting hole, the head section beingexposed outside the bottomend of the outer grip, the passage beingformed in the inner grip, the ratchet mechanism and the rotarycontrolling member being disposed at the head section.
 51. Screwdriverfor operating self-tightening screw as claimed in claim 39, wherein atleast two rib sections project from the top end of the grip, thescrewdriver further comprising a rotary cap, the rotary cap being formedwith a cavity inward extending from bottom face of the rotary cap,multiple receptacles being formed in the cavity for receiving variouskinds of screwdriver heads, the rotary cap being pivotally connectedwith the rib sections.